Industrial process and apparatus



United States Patent 3,352,122 INDUSTRIAL PROCESS AND APPARATUS Jerome H. Rothenberg, Dresher, Pa., and Charles B.

Hood, Jr., Columbus, Ohio, assignors to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 1, 1966, Ser. No. 530,838 5 Claims. (Cl. 62-45) ABSTRACT OF THE DISCLOSURE In a space simulation chamber pumping elements are arranged so that a super-cold pumping surface is reserved for pumping helium by placement of other pumping surfaces as a shield against straight-line movement of gas molecules toward the super-cold pumping surface.

This invention relates to a vacuum chamber for the simulation of outer space conditions. More specifically this invention relates to a pumping system for a vacuum chamber adapted to produce a vacuum of below torr.

In the simulation of cold black outer space conditions necessary for the observation and testing of equipment to be used in outer space, difficulty has been encountered in achieving vacuum in the range of 10- torr. in any large volume (500 cu. ft. and larger), and in fact in any practical, useful volume at all. Where it has been achieved in small volumes it has been inconvenient and difficult to get into or utilize test space and the facility has been extremely limited in application as a working tool. The pres-' ent invention overcomes many of these limitations and establishes a large workable volume within the chamber, accessible to the test object, to the parameters of cold black space, solar simulation, and extreme high vacuum in a practical, workable configuration.

In the prior attempts to create a vacuum, mechanical vacuum pumps and diffusion pumps have been used as well as cold surfaces, ion pumps and metal sublimators. It is well known that cold surfaces, ion pumps and metal sublimators are effective in taking particles of such gases as nitrogen, oxygen and helium, otherwise in movement in the chamber and taking them out of circulation to reduce the pressure within the chamber. One of the impediments in producing low vacuums has been that helium, a relatively large component of the atmosphere, has not been pumped efficiently by such pumping devices and its molecules have remained in movement limiting the vacuum within the chamber.

In accordance with the present invention a preferential system of pumping is established whereby a pumping means effective at pumping helium as well as other gases is disposed in a position relatively unaccessible to molecules within the working space of the chamber with the result that by the time the molecules reach this ultra-cool surface, particles other than helium have already been entrained or otherwise secured to other pumping surfaces so that the final cold surface is more or less reserved for the pumping of helium. In this manner a large percentage of the helium molecules in the chamber can be effectively pumped, thereby reducing the pressure to the ranges indicated.

Initially the invention contemplates for the securing of such low vacuum, the provision of a double-walled chamber whereby after roughing the volume within the outside and inside containers, the access between the inside and the outside containers can be closed, thereby maintaining at vacuum the volume within the inner container for pumping by in-chamber pumping means. The gas load within the inner container and the additional reduction of pressure within the chamber can be accomplished by the various other pumping devices, thereby making unnecessary the continued use of roughing devices.

Patented Nov. 14, 1967 Other objects of the invention will appear from the following description including the drawings wherein:

FIGURE 1 is a schematic sectional elevational view of an apparatus embodying the invention; and

FIGURE '2 is a fragmentary sectional view taken on the line 2-2 of FIGURE 1.

Referring more specifically to FIGURE 1, an apparatus embodying the invention is designated broadly as 10. It comprises an outer container 12 defining an outer chamber and an inner container 14 defining an inner chamber. The inner container is spaced from the outer container and supported thereby by means not shown in this schematic representation. Openings and appropriate transition pieces 16 and 18 are provided in the walls of the con tainers to utilize a solar simulator (not shown) which is directed at the mirror 20 suspended within the inner container. A support shelf 22 is mounted within the inner container for holding the specimen A which is to be observed under the conditions within the chamber. A valve 24 is provided in the wall of the inner container with operating means 26 extending through the walls of the outer container. The vacuum roughing device may be connected to a suitable flanged connection such as 28 in the wall of the outer container and is adapted to function when the valve 26 is in the open position.

A number of cold fins in the form of annular chevrontype baffles 30 are provided adjacent the top of the chember. Disposed centrally of the baffles is a solid horizontal wall 32, and disposed above the baffles are the ion pumps 34. An annular shroud 36 traced with liquid nitrogen, adapted to be the object of the titanium sublimating devices 38 is disposed inside the ion pumps 34. The entire container is traced with a cryogenic pumping system panel 39 and provided with slanted panels 39a with shields 39b. Annular chevron-type baifies 40 are disposed within the shroud.

In use the chevron-type annular baffles 30 are traced with liquid nitrogen, as is the chamber 14, and the panels 3%, and are maintained at the temperature of liquid nitrogen at a time immediately subsequent to the roughing period and. thereafter. The cryogenic panels 32, 39a and the chevron-type baflles 40 are cooled by a dense gas helium system and maintained at a temperature of 10 to 20 Kelvin. Disposed about the baffles 40 and extending down to the bafiles 30 is the annular shield 42 which is also maintained at the temperature of liquid nitrogen by being traced therewith. Plate 42a is also liquid-nitrogen traced. Disposed under the chevron-type bafiles 40 and within the shield 42 is an ultra-cold superpumping surface 44. The ultra-cold surface is preferably maintained in a temperature range of 2 to 10 K. by having dense gas or liquid helium circulated therein.

In a pumping procedure using the apparatus shown in FIGURE 1 the valve 24 is opened and the roughing pump connected to flanged connection 28 is activated to pump down the entire device to a pressure range of about 10- torr. Thereafter the blocking device or valve 24 is closed by means of the actuator 26 and the cold surfaces 30', 36, 39 and 39b are rendered effective as pumping devices by having the liquid nitrogen flow through them. Surfaces 32, 39a, 40 and 44 are activated and rendered cold by the dense gas helium refrigerant. In addition ion pumps 34 function in a manner well known in the art. Between them, cold surfaces 30, 39, 39a, 39b and 40*, and the ion pumps 34 pump nitirogen, oxygen, hydrogen and some helium. Titanium sublimators 38 contribute to the pumping by atttaching particles of nitrogen, oxygen, hydrogen, etc. onto the shroud 36 which is the object of their sublimation.

The pumps thus far described are not effective in pumping the large quantities of helium in the atmosphere within the chamber at the beginning of the process. The ultracold plate 44, traced with gaseous or liquid helium, is

effective at such pumping as well as at pumping the other gases. By screening the ultra-cold plate behind the other in-chamber pumps within the system, the pumping powers of the plate 44 are reserved for the helium molecules. These molecules not being settled on the cold surfaces of the ion pumps or by the titanium sublimator shroud 36 find their way to plate 44 and become attached. The molecules of the other gases will generally adhere to some of the other pumping surfaces.

As shown in the drawing the test object to be disposed in the chamber may be loaded by removing the lower end walls of the container at flanges 50. Such an arrangement is shown in detail in the co-pending application Ser. No. 531,898 of Jay L. Richman, filed Mar. 4, 1966 and assigned to our assignee. Access to the working space may also be had by removing the upper section of the containers at flanges 52. Obviously for a top loading unit the pump means at the upper end of the embodiment shown may be positioned at the lower end if desired or necessary.

As described the present invention provides a preferential pumping system by which the utlra-cold surface 44 is reserved for the pumping of the helium molecules present within the vacuum chamber. Were the plate 44 not shielded by other pumping surfaces, other gaseous molecules more easily pumped than helium by the various other pumping devices, would dissipate the pumping strength of the surface 44.

The invention in addition to the preferential pumping system already outlined provides for the isolation of the inner and outer containers so that the zone between containers may form a vacuum guard between the inner chamber and the atmosphere. At the same time when the shroud 24 is closed the means Within the container 14 are effective to take care of the outgassing and reduce the pressure within this container without the continued use of the roughing pump means.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

We claim:

1. A space simulation chamber having Working space therein and comprising a sealed outer container, an inner container within the outer container, removable means blocking passage from the outer container, removable means blocking passage from the outer container into the inner container pumping elements in said inner container and including an ion pump, titanium sublimator, cold surfaces and a super-cold pumping surface maintained at a temperature within the range of 2 to 4 Kelvin for pumping helium, shield means comprising pumping surfaces Within the inner container positioned to obstruct straightline movement of gas molecules from position in said inner container remote from the super-cold pumping surface to said super-cold pumping surface and to thereby reserve the pumping powers of said super-cold pumping surface for pumping helium, means maintaining said shield means at a temperature in a range of 10 to 20 Kelvin.

2. A chamber according to claim 1 wherein the pumping elements are arranged along an imaginary brokenline path with the working space at one end and the super-cold pumping surface at the other end of said chamher, with the other pumping elements therebetween to shield the super-cold pumping surface from the straight line movement of a gas molecule from the working space to the super-cold pumping surface, the super-cold pumping surface being better adapted to pump helium than the other pumping elements.

3. A vacuum chamber as described in claim 1 wherein each container comprises a shell having a removable lower end wall and said chamber is adapted to be loaded by removing said lower end walls.

4. A vacuum chamber as described in claim 1 wherein each container comprises a shell having a removable upper portion and said chamber is adapted to be loaded by removing said upper portion.

5. A chamber according to claim 1 wherein the ion pump is suitable for operating nude in extreme high vacuum.

References Cited UNITED STATES PATENTS 3,130,562 4/1964 Wood et a1 6255.5 3,149,775 9/1964 Pagano 62--268 3,175,373 3/1965 Holkeboer et al. 62 268 3,177,672 4/1965 Seelandt 62--55.5 3,262,279 7/1966 Moore 62-45 3,273,636 9/1966 Hickey et a1 62-268 LLOYD L. KING, Primary Examiner. 

1. A SPACE SIMULATION CHAMBER HAVING WORKING SPACE THEREIN AND COMPRISING A SEALED OUTER CONTAINER, AN INNER CONTAINER WITHIN THE OUTER CONTAINER, REMOVABLE MEANS BLOCKING PASSAGE FROM THE OUTER CONTAINER, REMOVABLE MEANS BLOCKING PASSAGE FROM THE OUTER CONTAINER INTO THE INNER CONTAINER PUMPING ELEMENTS IN SAID INNER CONTAINER AND INCLUDING AN ION PUMP, TITANIUM SUBLIMATOR, COLD SURFACES AND A SUPER-COLD PUMPING SURFACE MAINTAINED AT A TEMPERATURE WITHIN THE RANGE OF 2* TO 4* KELVIN FOR PUMPING HELIUM, SHIELD MEANS COMPRISING PUMPING SURFACES WITHIN THE INNER CONTAINER POSITIONED TO OBSTRUCT STRAIGHTLINE MOVEMENT OF GAS MOLECULES FROM POSITION IN SAID INNER CONTAINER REMOTE FROM THE SUPER-COLD PUMPING SURFACE TO SAID SUPER-COLD PUMPING SURFACE AND TO THEREBY RESERVE THE PUMPING POWERS OF SAID SUPER-COLD PUMPING SURFACE FOR PUMPING HELIUM, MEANS MAINTAINING SAID SHIELD MEANS AT A TEMPERATURE IN A RANGE OF 10* TO 20* KELVIN. 